Cabanas on the family beach are $499 for 6 people and $50 each for persons 7,8,9, and 10. Ten is the limit in the family beach cabanas. They give each person in your party a wrist band and do check for them. The wrist bands and a cute pop up paper model of your cabana will be placed in your stateroom the night before. Tubes, floating mats, bike rentals and srorkle gear are included in the price. One VERY nice thing about the family beach cabanas is that the beach in front of them is private in that only cabana users can use this part of the beach and even the ocean in front of it as it is also roped off. The rest of the family beach is very very overcrowded both on the sand and in the water. The chaise lounges are jammed right up against each other with no space to walk between them, and there are several rows of them. Families with very young children would have the benefit of having a shaded spot for napping infants and toddlers inside the cabanas. The cabanas on the adult beach do not have a private beach and have bushes in front of them. They include all of the things mentioned above except the snorkle gear. Since there would be no need for napping space for babies, the beach is not private, nor is the entire adult beach at Serenity Bay ever even close to being crowded, I think there is really no need to rent a cabana here. There are plenty of chaise lounges and hammocks and lots of space to spread out. You will have about six hours to spend on Castaway Cay, and if you are going to swim, walk the beach, snorkle, and ride bikes, you won't be in the cabana much. To sum up...there are many reasons to rent a cabana on the family beach, but very little reason to rent a cabana at the adult beach on Serenity Bay. Also, don't give up if there are no cabanas available online. Keep checking every day online because people do cancel them. And don't get all excited about free sodas, chips, and fruit in the cabana. The soda station is open nonstop over by the picnic area... And they have plenty of chips and fruit at the picnic.